Mold and molding apparatus using the same

ABSTRACT

A molding apparatus for patterning a workpiece includes a mold having a pattern to be transferred to the workpiece, with the pattern including recesses, a first support member for supporting the mold, and a second support member, arranged opposite to the first support member, for supporting the workpiece. A pressing mechanism brings the first and second support members close to each other and presses the mold and the workpiece together so as to transfer, to the workpiece, the pattern on the mold. Recessed portions are provided on at least one of a surface of the mold on the first support member side, a region of the first support member, and a region of the second support member. The recessed portions correspond to recesses in the pattern of the mold.

This is a continuation of application Ser. No. 11/058,195, filed on Feb.16, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a press molding apparatus, a pressmold, and a press molding method, for transferring the features of amold to a work (workpiece) under the application of pressure.

2. Description of the Related Art

In recent years, micro-fabrication technology for press transferringfine structures on a mold to a workpiece, such as resin or metal, havebeen developed and become a focus of attention. This technology, callednano-imprint or nano-embossing, has a resolution on the order of severalnanometers. In addition, it can mold 3D structures on a wafer by oneoperation. For these reasons, this technology is expected to beapplicable to a wide variety of fields, such as the next-generationsemiconductor fabrication, the fabrication of optical elements likephotonic crystals, and the fabrication of biochips such as μ-TAS chips.

There have also been proposed methods of pressing a mold into a resiston a semiconductor wafer to create an imprint pattern so as to produce apattern on the semiconductor wafer through the process of ion milling.

There is disclosed a method of pressing a mold into a resist to mold theresist and etching the resist pattern to form holes in a wafer on whichthe resist has been carried (U.S. Pat. No. 5,772,905).

The following describes the current state of the above-mentioned moldingtechnology with reference to FIGS. 4 to 6.

FIG. 4 shows a typical example of the structure of the prior arttechnology. A mold 104 is typically micro-fabricated on a wafer of Si orSiO₂ by EB lithography, FIB, X-ray lithography, etc, or replicated by Nielectroforming. A work is typically resin 105 coated on a wafer 106 of adesired material, or a resin plate. The mold 104 and the work(workpiece) are sandwiched between a mold pressing member 103 and awafer pressing member 107, and pressed together by means of a pressmechanism (not shown).

FIG. 5 shows a pressed state in the structure of FIG. 4. In this case,the pressing members, the mold 104, and the wafer 106 are partiallydeformed, crushing a large recess almost flat. As a result, since thework is molded as shown in FIG. 6, the accuracy of shaping the work isreduced. Such a phenomenon becomes noticeable as the molding pressureincreases or the recessed area is shallower.

It is therefore desired to have a molding technique capable oftransferring features with a high degree of precision for finerfabrication by reducing the deformation of a mold and a work in thevicinity of a recess on the mold.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a mold, a moldingapparatus, and the like, which can reduce the deformation of the moldand a work due to a pressing force.

In order to solve the above-mentioned problem, the present inventionuses the following means.

That is, according to the present invention, there is provided a moldingapparatus for patterning a workpiece using a mold. The apparatusincludes a first support member for supporting the mold, a secondsupport member, arranged opposed to the first support member, forsupporting the workpiece, and press means for bringing the first andsecond support members close to each other to press the mold and theworkpiece together so as to transfer, to the workpiece, the pattern ofrecessed and raised features formed on the mold.

In this structure, recessed portions are provided in positions,corresponding to recesses in the pattern of the mold, on at least one ofthe surface of the mold on the support member side, the region orsurface of the first support member on the mold side, and the region orsurface of the second support member on the workpiece side.

It is preferable that the recesses provided in positions, correspondingto the recessed and raised features of the mold, on the surface(s)selected from the surface of the mold on the support member side, thesurface of the first support member on the mold side, and the surface ofthe second support member on the workpiece side, be filled with amaterial having a lower Young's modulus than the material that forms thefeatures surrounding each recess (that is, the raised features).

According to the present invention, there is also provided a mold foruse in patterning the work surface of a workpiece. The mold has recessesprovided on the opposite side of the mold surface in positionscorresponding to the recessed features of the mold surface.

According to the present invention, the recesses corresponding to therecessed features of the mold surface are provided in the press member(first or second support member), or on the backside of the mold. Inother words, hollow portions are provided in the paths of transmissionof molding force to prevent in part the transmission of the moldingforce. This prevents the deformation of the mold and the work in therecessed areas of the mold surface, enabling the transfer of thefeatures on the mold to the work with a high degree of precision.Instead of the hollow portions, such a material to prevent thetransmission of force may also be used. This can achieve precisetransfer even in the case where the precision of the mold and the workis inadequate.

Further features and advantages of the present invention will becomeapparent from the following description of exemplary embodiments (withreference to the attached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view for explaining the structure of anapparatus according to a first embodiment of the present invention.

FIG. 2 is a cross sectional view for explaining the structure of anapparatus according to a second embodiment of the present invention.

FIG. 3 is a cross sectional view for explaining the structure of anapparatus according to a third embodiment of the present invention.

FIG. 4 is a cross sectional view for explaining the problem of the priorart technology.

FIG. 5 is a cross sectional view for explaining the problem of the priorart technology.

FIG. 6 is a cross sectional view for explaining the problem of the priorart technology.

DESCRIPTION OF THE EMBODIMENTS

In preferred embodiments of the present invention, any of theabove-mentioned structures is applied in such a manner that hollowportions are provided in the paths of transmission of molding force, forexample, by providing recesses in positions, corresponding to recessesof the mold surface, on the backside of the mold or in a pressingmember, for preventing in part the transmission of the molding force.This helps to prevent the deformation of the mold and the work in therecessed areas of the mold surface, enabling the transfer of thefeatures on the mold to the work with a high degree of precision.Instead of the hollow portions, such a material to prevent thetransmission of force can also be used.

When the recesses are provided on the backside of the mold, it ispreferable to provide them with respect to the recesses of the moldsurface in the direction parallel to the direction of the molding force.

These techniques may be applied restrictively to only wide recesses onthe mold surface. In this case, since the hollow portions are formed inlimited areas, the manufacturing cost can be reduced.

In particular, when the hollow portions are provided in the pressingmember, the pressing member can be reused for other molds having thesame features, enabling a cost reduction. On the other hand, when theyare provided in the mold, position errors due to misalignment or thermaldeformation can be reduced, thereby improving molding precision.

A material with a low Young's modulus may also be placed between thepressing member and the mold or work. In this case, in addition to theabove-mentioned effects, the molding force can be distributed evenlyeven though the precision of the shape of each member or the precisionof the apparatus is inadequate. This makes it possible not only toreduce the cost of manufacturing the member, but also to improve moldingprecision.

According to the present invention, recesses similar to the recessesformed in the mold, or master, are provided in corresponding positionsto those in the mold.

The present invention covers the cases where the recesses are provided(1) in a mold support member 103 (mold pressing member in FIG. 1), (2)on the backside of the mold 104 (FIG. 2), and (3) in a work supportmember 107 (work pressing member in FIG. 1). Of course, the recesses donot need to be provided in all of the mold support member, the mold, andthe work support member. It is appropriately selected from (1) to (3)where the recesses are provided. The recesses can be provided in thefollowing locations or combinations of locations: (1), (1)+(2), (1)+(3),(1)+(2)+(3), (2), (2)+(3), and (3). In either of the cases (1), (2), and(3), or combinations of them, it is preferable that recessed and raisedfeatures be provided in corresponding positions to the recessed andraised areas of the mold. The “corresponding positions” meanscorresponding positions in the pressing direction to apply pressurebetween the mold and the workpiece.

Further, in either of the cases (1), (2), and (3) or combinations ofthem, the recessed and raised features do not need to be provided in allpositions corresponding to the recessed and raised areas of the mold onthe workpiece side.

The depths of the recesses do not need to be exactly equal to the depths(step heights) of the mold on the workpiece side. It is preferable,however, that the support member or mold as in the case of (1), (2), or(3), or in any combination of (1), (2), and (3), have recesses incorresponding positions to the recesses of the mold that face the worksurface.

It is also preferable that the support member or mold as in the case of(1), (2), or (3), or in any combination of (1), (2), and (3), haveraised features in corresponding positions to the raised areas of themold that face the work surface.

The above describes the case where a plate-shaped mold is used, but thepresent invention is also applicable to a roll-shaped mold, that is, amold having raised and recessed features to be transferred to thesurface of a cylinder.

EMBODIMENTS First Embodiment

The first embodiment of the present invention will now be described withreference to FIG. 1.

As shown in FIG. 1, the mold 104 is arranged opposed to the wafer 106coated with resin 105. The mold 104 is mounted on the mold pressingmember 103, while the wafer 106 is mounted on the wafer pressing member107. Both of the pressing members are connected to each other through apress mechanism 102 and an apparatus frame or casing 101 that receives areactive force from the press mechanism 102. The press mechanism 102applies pressure between the mold 104 and the wafer 106 to transfer thesurface features of the mold 104 into the resin 105. The press mechanism102 moves the mold in FIG. 1, but it may move the work, or both.

Grooves of 50 μm deep are formed by precision cutting on the surface ofthe mold pressing member 103 that faces the backside of the mold 104.The pattern of the grooves may be the same as the pattern on the surfaceof the mold 104. In this case, however, since small recesses of the mold104 are deformed by small amounts, only the grooves corresponding towide recesses are formed in consideration of manufacturing cost. Itdepends on the required precision of the grooves to be formed. In theembodiment, the grooves are formed corresponding to recesses whosewidth-to-depth ratio exceeds 20:1 in their narrowest position on themold 104.

When the mold pressing member 103 as structured above is used to pressthe mold, the grooves serve as the hollow portions in the paths oftransmission of molding force, so that the transmission of the moldingforce to the recesses on the surface of the mold 104 can be reduced,thereby transferring the features on the mold 104 into the resin 105with a high degree of precision. This also prevents a waste of moldingforce.

The pressing member in which the grooves are formed is not limited tothe mold pressing member 103. The grooves may be formed in the waferpressing member 107. For example, if the mold 104 and the wafer 106 varyconsiderably in material and thickness, they may differ in degree ofdeformation in the recesses. In such a case, the grooves may be formedin one pressing member, which is larger in degree of deformation thanthe other, or at symmetrically opposed positions of both pressingmembers.

According to the embodiment, when the surface features of the mold 104do not change, if the mold is replaced with another due to mold breakageor degradation, the mold pressing member 103 can be reused. This isparticularly suitable for mass production.

Second Embodiment

The second embodiment of the present invention will now be describedwith reference to FIG. 2.

As shown in FIG. 2, the mold 104 is arranged opposed to the wafer 106coated with the resin 105. The mold 104 is mounted on the mold pressingmember 103, while the wafer 106 is mounted on the wafer pressing member107. Both of the pressing members are connected to each other throughthe press mechanism 102 and the casing 101 that receives a reactiveforce from the press mechanism 102. Further, a heater 201 is inserted inboth of the pressing members for the purpose of heating the mold 104 andthe resin 105. In operation, after the mold 104 and the wafer 106 areheated to a glass transition point of the resin 105, the press mechanism102 applies pressure between the mold and the wafer to transfer thesurface features of the mold 104 into the resin 105.

The mold 104 is, for example, manufactured as follows: A symmetricalfront-back pattern is formed on both polished sides of Si wafer byphotolithography or X-ray lithography using two masks that are mirrorimages of each other. In such a mold 104, the backside of a recess isalso a recess. Therefore, when the surface of the mold 104 is pressed inthe molding process, the recesses on the backside serve as the hollowportions in the paths of transmission of molding force, so that thetransmission of the molding force to the recesses on the surface of themold 104 can be reduced, thereby transferring the features on the mold104 into the resin 105 with a high degree of precision. This alsoprevents a waste of molding force.

The method of making the mold 104 is not limited to the above-mentionedmethod. The symmetrical front/back pattern may also be formed using anyother micro-fabrication technique, such as FIB (Focused Ion Beam)lithography or EB (Electron Beam) lithography. Like in the firstembodiment, micro-machined areas on the backside may be restrictivelyselected. Further, the processed depth on the backside can beappropriately changed. For example, if the resin 105 is highlyshapeable, the pattern on the backside may be made shallower.

In the embodiment, the mold 104 itself has portions for preventing inpart the transmission of molding force. Since this structure is notaffected by mounting errors, it is suitable for nano-patterningprocesses, especially for high-precision nano-fabrication processes.Further, since there is no difference in thermal expansion coefficientto cause misalignment, it is particularly suitable for nano-fabricationprocesses involving temperature changes, as well as the above-mentionedprocesses. Furthermore, since the features to be molded can be changedonly by changing the mold 104, it is also suitable for large-item,small-scale production.

Third Embodiment

The third embodiment of the present invention will now be described withreference to FIG. 3.

As shown in FIG. 3, the mold 104 is arranged opposed to the wafer 106coated with the resin 105. The mold 104 is mounted on the mold pressingmember 103, while the wafer 106 is mounted on the wafer pressing member107 through rubber 301. Both of the pressing members are connected toeach other through the press mechanism 102 and the casing 101 thatreceives a reactive force from the press mechanism 102. The pressmechanism 102 applies pressure between the mold 104 and the wafer 106 totransfer the surface features of the mold 104 into the resin 105.

Grooves of 100 μm deep are formed by precision cutting on the surface ofthe wafer pressing member 107 that faces the wafer 106. Each of thegrooves is positioned directly below each recess of the mold 104. Thepattern of the grooves may be the same as the pattern on the surface ofthe mold 104, but for the same reason as in the first embodiment, thegrooves to be formed are restricted to only the areas corresponding tothe recesses whose width-to-depth ratio exceeds 20:1 in their narrowestposition on the mold 104. The surface on which the grooves have beenformed is then coated with liquid rubber and cured. The thickness of therubber 301 in the non-groove area is 100 μm.

When the wafer pressing member 107 as structured above is used toperform press molding, since the rubber in the grooves has lowcompressibility, it reduces the transmission of the molding force to therecesses of the mold 104, thereby enabling the transfer of the featureson the mold 104 into the resin 105 with a high degree of precision.

Although in the embodiment the grooves are formed in the wafer pressingmember 107 with the rubber 301 arranged thereon, they may be formed inthe mold pressing member 103 as in the first embodiment, or in bothmembers in the same manner. Further, if the rubber 301 is placed betweenthe mold 104 in the second embodiment and the mold pressing member 103,the same effects can be obtained. In the embodiment, the rubber 301 ismade by curing liquid rubber, but a slice of rubber may be mountedinstead.

Any other material with low Young's modulus, such as various kinds ofpolymers or soft metal like indium, is selectable as appropriate insteadof the rubber 301.

In the embodiment, the rubber 301 can distribute the molding force onthe non-groove area evenly. Therefore, in addition to the applicationsshown in the first and second embodiments, it is suitable for a casewhere the shape precision of the components, such as the mold pressingmember 103, the mold 104, the wafer 106, and the wafer pressing member107, is inadequate due to limitations of fabrication technology andeconomics, or the precision of the apparatus is so inadequate that themold 104 and the wafer 106 cannot be pressed while maintaining adequatehorizontal alignment between them.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed embodiments. On the contrary, the invention isintended to cover various modifications and equivalent arrangementsincluded within the spirit and scope of the appended claims. The scopeof the following claims is to be accorded the broadest interpretation soas to encompass all such modifications and equivalent structures andfunctions.

This application claims priority from Japanese Patent Application No.2004-044727 filed Feb. 20, 2004, which is hereby incorporated byreference herein.

1. A method of patterning a workpiece, comprising the steps of:preparing a mold having a pattern comprising a first recessed portion tobe transferred to the workpiece, setting the mold on a first supportmember for supporting the mold, placing the workpiece on a secondsupport member arranged opposite to the first support member, andtransferring the pattern on the mold to the workpiece by bringing thefirst support member and the second support member relatively close toeach other, wherein a second recessed portion corresponding to a shapeof the first recessed portion is provided in at least one of a surfaceof the mold on the first support member side, a region of the firstsupport member, and a region of the second support member, wherein thesecond recessed portion is provided in the surface of the mold on thefirst support member side.
 2. A patterning method according to claim 1,wherein the first recessed portion has a wide recess and a narrowrecess, and the second recessed portion corresponds to a shape of thewide recess.
 3. A patterning method according to claim 1, wherein thesecond recessed portion contains a material with a Young's modulus lowerthan that of a material surrounding the second recessed portion.